Spin-on antireflective coating for integration of patternable dielectric materials and interconnect structures

ABSTRACT

The present invention provides a method of fabricating an interconnect structure in which a patternable low-k material replaces the need for utilizing a separate photoresist and a dielectric material. Specifically, this invention relates to a simplified method of fabricating single-damascene and dual-damascene low-k interconnect structures with at least one patternable low-k dielectric and at least one inorganic antireflective coating. In general terms, a method is provided that includes providing at least one patternable low-k material on a surface of an inorganic antireflective coating that is located atop a substrate. The inorganic ARC is liquid deposited and comprises a polymer that has at least one monomer unit comprising the formula M-R 1  wherein M is at least one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La and R 1  is a chromophore. At least one interconnect pattern is formed within the at least one patternable low-k material and thereafter the at least one patternable low-k material is cured. The inventive method can be used to form dual-damascene interconnect structures as well as single-damascene interconnect structures.

FIELD OF THE INVENTION

The present invention relates to a patternable dielectric interconnectstructure with improved lithography that is a part of integratedcircuits and microelectronic devices. Specifically, the presentinvention relates to a single-damascene and dual-damascene interconnectstructure that comprises a patternable low-k material and anantireflective coating that is deposited from the liquid phase. Thepresent invention also relates to a method of fabricating suchinterconnect structures.

BACKGROUND OF THE INVENTION

It is widely known that the speed of propagation of interconnect signalsis one of the most important factors controlling overall circuit speedas feature sizes are reduced and the number of devices per unit area aswell as the number of interconnect levels are increased. Throughout thesemiconductor industry, there has been a strong drive to increase theaspect ratio (i.e., height to width ratio) and to reduce the dielectricconstant, k, of the interlayer dielectric (ILD) materials used toelectrically insulate the metal conductive lines. As a result,interconnect signals travel faster through conductors due to a reductionin resistance-capacitance (RC) delays.

State-of-the-art semiconductor chips employ copper (Cu) as theelectrical conductor and inorganic organosilicates as the low dielectricconstant (low-k) dielectric, and have up to twelve levels of Cu/low-kinterconnect layers. These Cu/low-k interconnect layers are fabricatedwith an iterative additive process, called dual-damascene, whichincludes several processing steps. For example, a typical dual-damasceneprocess includes film deposition, patterning by lithography and reactiveion etching, liner deposition, Cu metal fill by electrochemical plating,and chemical-mechanical polishing of excessive Cu metal; these steps aredescribed in greater detail in the following paragraphs.

When fabricating integrated circuit wiring within a multi-layeredscheme, an insulating or dielectric material, e.g., silicon oxide or alow-k insulator will normally be patterned with several thousandopenings to create conductive line openings and/or via openings usingphoto patterning and plasma etching techniques, e.g., photolithographywith subsequent etching by plasma processes. The via openings aretypically filled with a conductive metallic material, e.g., aluminum,copper, etc., to interconnect the active and/or passive elements of theintegrated circuits. The semiconductor device is then polished to levelits surface.

A continuous cap layer is then normally deposited over the planarizedsurface featuring the dielectric material and conductive metallicmaterial. Next, a dielectric material is deposited over the continuouscap layer, via and line openings are created within the dielectric layeras before, another conductive metallic material is deposited within theopenings and another continuous cap layer is deposited thereon. Theprocess is repeated to fabricate a multi-layer interconnect wiringsystem. The multi-layer interconnect system built thereby is referred toin the art as a dual-damascene integration scheme.

Unfortunately, the strategy to introduce low-k materials (typicallydielectrics whose dielectric constant is below that of silicon oxide)into advanced interconnects is difficult to implement due to the newmaterials chemistry of the low-k materials that are being introduced.Moreover, low-k dielectrics exhibit fundamentally weaker electrical andmechanical properties as compared to silicon oxide. Moreover, the low-kdielectric alternatives are typically susceptible to damage during thevarious interconnect processing steps. The damage observed in the low-kdielectric materials is manifested by an increase in the dielectricconstant and an increased moisture uptake, which may result in reducedperformance and device reliability.

One way to overcome the integration challenges of low-k materials is toprotect these low-k dielectric materials by adding at least onesacrificial hardmask layer onto a surface of the low-k dielectricmaterial. While the hardmask layer serves to protect the low-k material,the presence of the sacrificial hardmask layer adds enormous processcomplexity as more film deposition, pattern transfer etch, and removalof hardmask layers are needed.

A state-of-the-art back-end-of-the-line (BEOL) integration process,called a low temperature oxide (LTO) process, employs up to eight layersof sacrificial hardmask materials to fabricate a two-layerdual-damascene interconnect structure.

For example, a via-first LTO integration for forming a dual-damasceneinterconnect includes the steps of: depositing a dielectric material ona substrate including a patterned conductor; forming at least one via insaid dielectric material, such that at least one of the vias ispositioned over the patterned conductor; depositing a layer ofplanarizing material on the dielectric material and in the via;depositing a layer of barrier material on the layer of planarizingmaterial; depositing at least one layer of imaging material on the layerof barrier material; forming at least one trench in the imagingmaterial, barrier material and planarizing material, such that the atleast one trench is positioned over the via; removing the imagingmaterial, either after or concurrently with forming the trench in theplanarizing material; transferring the at least one trench to thedielectric material, such that at least one of the trenches ispositioned over the via; removing the barrier material, either after orconcurrently with transferring the at least one trench to the dielectricmaterial; and removing the planarizing material.

A line-first LTO integration for forming a dual-damascene interconnectstructure includes the steps of: depositing a dielectric material on asubstrate including a patterned conductor; forming at least one trenchin the dielectric material, such that the at least one trench ispositioned over the patterned conductor; depositing a layer ofplanarizing material on the dielectric material and in the trench;depositing a layer of barrier material on the layer of planarizingmaterial; depositing at least one layer of imaging material on the layerof barrier material; forming at least one via in the imaging material,barrier material and planarizing material, such that at least one of thevias is positioned over the trench and the patterned conductor; removingthe imaging material, either after or concurrently with forming the viain the planarizing material; transferring the at least one via to thedielectric material, such that at least one of the vias is positionedover the trench and the patterned conductor; removing the barriermaterial, either after or concurrently with transferring the at leastone via to the dielectric material; and removing the planarizingmaterial.

The integration schemes, such as the LTO one mentioned above, are verycomplex, inefficient, and costly. For example, the via-first LTOintegration scheme requires ten layers of films and twenty-one processsteps to form a two-layer dual-damascene dielectric structure. In otherwords, 80% of films are not needed in the final interconnect structure.

Although immensely popular in semiconductor manufacturing, the prior artdual-damascene integration scheme described above suffers from severaldrawbacks including:

-   -   (I) First, it constitutes a significant portion of manufacturing        cost of advanced semiconductor chips as many layers, up to        twelve layers for the state-of-the-art chips, are required to        connect the minuscule transistors within a chip and to the        printed circuit board.    -   (II) Second, it is a yield detractor as the many layers of films        required to form the interconnects generate chances for defect        introduction and, thus, degrade manufacturing yields.    -   (III) Third, it is very inefficient and embodies enormous        complexity. The current dual-damascene integration scheme        requires many sacrificial films (80% of the film stack) to        pattern and protect the fragile interlayer dielectric films from        damage during processing. These sacrificial patterning and        protective films have to be removed after patterning and copper        plating.    -   (IV) Fourth, the performance gain by introduction of new lower-k        materials is often offset by the needs for higher-k        non-sacrificial materials, such as a cap layer, a hardmask        layer, or a thicker copper barrier layer.    -   (V) Fifth, the prior art complex dual-damascene process        lengthens manufacturing turn-around time and R&D development        cycle.    -   (VI) Sixth, the plasma etching process is an expensive and often        unreliable process and requires significant up-front capital        investment.

In view of the above, there is a need to simplify the formation ofinterconnects (single-damascene and dual-damascene) including low-kdielectrics for cost-saving and manufacturing efficiency.

SUMMARY OF THE INVENTION

The problems described above in prior art processes of fabricatinginterconnect (single-damascene and dual-damascene) structures are solvedby using a dramatically simplified integration method of this invention.The present invention thus relates to a method of forming interconnectstructures that are part of integrated circuits and microelectronicdevices with patternable dielectrics combined with an antireflectivecoating that is formed from a liquid phase.

This invention circumvents the prior art drawbacks of currentintegration by combining the functions of a photoresist and a dielectricmaterial into one material. This one material, called aphoto-patternable low-k dielectric (or patternable low-k material forshort), acts as a photoresist during the lithographic patterningprocess, and as such, no separate photoresist is required. Afterlithographic patterning, the patternable low-k dielectric issubsequently converted into a low-k material during a post patterningcure. In this way, the inventive method avoids plasma etching and thecomplex sacrificial film stack and processes required for patterning.

In the inventive method, an antireflective coating layer is required forpatterning of a patternable low-k material via lithography.Unfortunately, conventional organic antireflective coatings aregenerally not suitable for the lithography of a patternable low-kmaterial as the antireflective coating layer is a permanent part of theinterconnect structure. These organic antireflective coatings typicallycannot withstand high temperature processes such as, for example, duringeither the curing of the patternable low-k dielectric or annealing ofthe interconnect metal.

Thus, the present invention provides an antireflective coating (ARC) forlithography and interconnect integration of patternable low-k materials.The antireflective coating that is employed in the present invention isa permanent part of the interconnect structure and is formed by liquiddeposition including, for example, spin-on, spray coating, evaporation,chemical solution deposition, dip coating or brush coating.

In particular, the inventive ARC is formed by liquid phase deposition ofa liquid composition that includes an inorganic precursor that has atomsof M, C and H, wherein M is at least one of Si, Ge, B, Sn, Fe, Ta, Ti,Ni, Hf and La. The inorganic precursor used in forming the ARC mayoptionally include atoms of O, N, S, F or mixtures thereof. In someembodiments, M is preferably Si. The liquid composition also includes,in addition to the inorganic precursor, a chromophore, a cross-linkingcomponent, an acid generator and a solvent.

Once the liquid composition is deposited and subsequently cured, an ARCis formed including at least one monomer unit in which the M of theinorganic precursor is bonded to the chromophore; hereinafter thismonomer unit is written as M-R¹ wherein M is defined above and R¹ is thechromophore. In this formula, M within the monomer unit may also bebonded to organic ligands including atoms of C and H, a cross-linkingcomponent, another chromophore or mixtures thereof. The organic ligandsmay further include one of O, N, S and F. When the organic ligand isbonded to M, it is bonded to M through C, O, N, S, or F.

In some embodiments of the present invention, the liquid compositionincludes at least one first monomer unit in which the M of the inorganicprecursor is bonded to the chromophore (M-R¹) and at least one secondmonomer unit in which another M of the inorganic precursor is bonded toa cross-linking component (i.e., M′-R²), wherein M or M′ each is atleast one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La. M and M′ may bethe same or different elements. In these two formulae, M and M′ withinthe monomer unit may be also be bonded to organic ligands includingatoms of C and H, a cross-linking component, a chromophore or mixturesthereof. The organic ligands may further include one of O, N, S and F.When the organic ligand is bonded to M and M′, it is bonded to M or M′through C, O, N, S, or F.

The liquid ARC composition comprising M-R′ or M-R¹ and M′-R² may furthercomprise at least one additional component, including a separatecrosslinker, an acid generator or a solvent.

Specifically, this invention relates to a simplified method offabricating single-damascene and dual-damascene low-k interconnectstructures with at least one patternable dielectric. In general termsand in one aspect of the present invention, a method is provided thatcomprises:

providing at least one patternable low-k material on a surface of aninorganic antireflective coating (ARC) that is located atop a substrate,said inorganic ARC is liquid deposited and comprises a polymer that hasat least one monomer unit comprising the formula M-R¹ wherein M is atleast one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La and R¹ is achromophore;

forming at least one interconnect pattern within said at least onepatternable low-k material, said at least one interconnect pattern isformed without utilizing a separate photoresist material; and

curing said at least one patternable low-k material and the inorganicARC into materials having a dielectric constant of not more than 4.3 and7.0, respectively.

In some embodiments of this method of the present invention, M withinthe monomer unit may also be bonded to organic ligands including atomsof C and H, a cross-linking component, another chromophore or mixturesthereof. The organic ligands may further include one of O, N, S and F.When the organic ligand is bonded to M, it is bonded to M through C, O,N, S, or F.

In other embodiments of the present invention, the ARC may also includeat least one second monomer unit, in addition to the at least onemonomer unit represented by the formula M-R¹. When present, the at leastone second monomer unit has the formula M′-R², wherein R² is across-linking agent and M′ is at least one of Si, Ge, B, Sn, Fe, Ta, Ti,Ni, Hf and La. M and M′ may be the same or different elements. In thesetwo formulae, M and M′ within the monomer unit may be also be bonded toorganic ligands including atoms of C and H, a cross-linking component, achromophore or mixtures thereof. The organic ligands may further includeone of O, N, S and F. When the organic ligand is bonded to M and M′, itis bonded to M or M′ through C, O, N, S, or F.

The liquid ARC composition comprising M-R¹ or M-R¹ and M′-R² may alsocomprise at least one additional component, including a separatecrosslinker, an acid generator or a solvent.

In some embodiments of the present invention, a dielectric cap is formedon the substrate prior to forming the inorganic ARC by liquiddeposition.

The present invention also contemplates a step of forming contact holesthrough the antireflective coating or material stack including theantireflective coating and the dielectric cap after forming theinterconnect patterns.

In yet a further embodiment of the present invention, a conductivematerial such as Al, Cu, or a Cu alloy is formed into the interconnectpatterns. A planarization process such as chemical mechanical polishingmay follow the step of filling the interconnect patterns.

In an even further embodiment of the present invention, a dielectric capis formed atop the cured low-k material after filling the interconnectpatterns with a conductive material and removing any excessiveconductive material.

In any of the embodiments mentioned above, the interconnect patterns maycomprise via openings, line openings, a combination of via openingslocated beneath line openings or a combination of line openings locatedbeneath via openings. In one embodiment, it is preferred to have viaopenings located beneath line openings. It is noted that in the presentinvention each individual pair of line/via openings or via/line openingsis interconnected.

The present invention contemplates the use of positive-tone patternablelow-k materials, negative-tone patternable low-k materials or anycombination thereof.

In another aspect of the present invention, the present inventionprovides a simplified method of fabricating dual-damascene low-kinterconnect structures with at least one negative-tone patternablelow-k dielectric and/or at least one positive-tone patternable low-kdielectric. This aspect of the present invention includes the steps of:

providing a first patternable low-k material on a surface of aninorganic antireflective coating (ARC) that is located atop a substrate,said inorganic ARC is liquid deposited and comprises a polymer that hasat least one monomer unit comprising the formula M-R¹ wherein M is atleast one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La and R¹ is achromophore;

forming first interconnect patterns within the patternable low-kmaterial without a separate photoresist material;

providing a second patternable low-k material on top of the firstpatternable low-k material including said first interconnect patterns;

forming second interconnect patterns within said second patternablelow-k material without a separate photoresist material; and

curing said at least one patternable low-k material and the inorganicARC into materials having a dielectric constant of not more than 4.3 and7.0, respectively.

In some embodiments of this method of the present invention, M withinthe monomer unit may also be bonded to organic ligands including atomsof C and H, a cross-linking component, another chromophore or mixturesthereof. The organic ligands may further include one of O, N, S and F.When the organic ligand is bonded to M, it is bonded to M through C, O,N, S, or F.

In other embodiments of the present invention, the ARC may also includeat least one second monomer unit, in addition to the at least onemonomer unit represented by the formula M-R¹. When present, the at leastone second monomer unit has the formula M′-R², wherein M′ is at leastone of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La, and R² is across-linking agent. M and M′ may be the same or different elements. Inthese two formulae, M and M′ within the monomer unit may be also bebonded to organic ligands including atoms of C and H, a cross-linkingcomponent, a chromophore or mixtures thereof. The organic ligands mayfurther include one of O, N, S and F. When the organic ligand is bondedto M and M′, it is bonded to M or M′ through C, O, N, S, or F.

The liquid ARC composition comprising M-R¹ or M-R¹ and M′-R² may alsocomprise at least one additional component, including a separatecrosslinker, an acid generator or a solvent.

In another embodiment of the present invention, a dielectric cap isformed on top of the substrate prior to forming the ARC.

The present invention also contemplates a step of forming contact holesthrough the antireflective coating or material stack including theantireflective coating and the dielectric cap after forming the firstand second interconnect patterns.

In yet other embodiments of the present invention, a curing step isperformed after providing the first interconnect patterns to the firstpatternable low-k material.

In yet a further embodiment of the present invention, a conductivematerial such as Al, Cu, or a Cu alloy is formed into the first andsecond interconnect patterns. A planarization process such as chemicalmechanical polishing may follow the step of filling the first and secondinterconnect patterns.

In an even further embodiment of the present invention, a dielectric capis formed atop the cured second patternable low-k material after fillingthe first and second interconnect patterns with a conductive material.

In any of the embodiments mentioned above, the first interconnectpatterns may comprise via openings, while the second interconnectpatterns may comprise line openings. This embodiment is preferred overan embodiment in which the first interconnect patterns comprise lineopenings and the second interconnect patterns comprise via openings.

This invention also relates to a simplified method of fabricatingsingle-damascene low-k interconnect structures with negative-tone orpositive-tone patternable low-k dielectrics. This aspect of the presentinvention comprises the steps of:

providing a patternable low-k material on a surface of an inorganicantireflective coating (ARC) that is located atop a substrate, saidinorganic ARC is liquid deposited and comprises a polymer that has atleast one monomer unit comprising the formula M-R¹ wherein M is at leastone of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La and R¹ is a chromophore;

forming interconnect patterns within the patternable low-k materialwithout a separate photoresist material; and

curing said patternable low-k material and the inorganic ARC intomaterials having a dielectric constant of not more than 4.3 and 7.0,respectively.

In some embodiments of this method of the present invention, M withinthe monomer unit may also be bonded to organic ligands including atomsof C and H, a cross-linking component, another chromophore or mixturesthereof. The organic ligands may further include one of O, N, S and F.When the organic ligand is bonded to M, it is bonded to M through C, O,N, S, or F.

In other embodiments of the present invention, the ARC may also includeat least one second monomer unit, in addition to the at least onemonomer unit represented by the formula M-R¹. When present, the at leastone second monomer unit has the formula M′-R², wherein M′ is at leastone of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La, and R² is across-linking agent. M and M′ may be the same or different elements. Inthese two formulae M and M′ within the monomer unit may be also bebonded to organic ligands including atoms of C and H, a cross-linkingcomponent, chromophore or mixtures thereof. The organic ligands mayfurther include one of O, N, S and F. When the organic ligand is bondedto M and M′, it is bonded to M or M′ through C, O, N, S, or F.

The liquid ARC composition comprising M-R¹ or M-R¹ and M′-R² may alsocomprise at least one additional component, including a separatecrosslinker, an acid generator or a solvent.

In another embodiment of the present invention, a dielectric cap isformed on top of the substrate prior to forming the ARC.

The present invention also contemplates a step of forming contact holesthrough the antireflective coating or material stack including theantireflective coating and the dielectric cap after forming theinterconnect patterns.

In yet a further embodiment of the present invention, a conductivematerial such as Al, Cu, or a Cu alloy is formed into the interconnectpatterns. A planarization process such as chemical mechanical polishingmay follow the step of filling the interconnect patterns.

In an even further embodiment of the present invention, a dielectric capis formed atop the cured patternable low-k material after filling theinterconnect patterns with a conductive material.

In any of the embodiments mentioned above, the interconnect patterns maycomprise via openings or line openings.

This patternable low-k/inorganic ARC method of present inventiondramatically reduces the complexity in the fabrication of currentinterconnect structures. The photoresist used in the prior artintegration is no longer needed. In addition to not requiring a separatephotoresist, the present invention also does not utilize a plasmaetching step for patterning as also required in the prior artinterconnect processing schemes. It is further noted that the inventivemethod reduces the number of layers required to fabricate theinterconnect structure and, as such, the present invention reduces thetime and cost of fabricating interconnect structures as compared toprior art processes.

In addition to the methods described above, the present invention alsorelates to interconnect structures which include the patternable low-kdielectric material in a cured state; in the cured state the patternablelow-k material serves as the interconnect dielectric. In general terms,the present invention provides an interconnect structure comprising atleast one patterned and cured low-k dielectric material located on asurface of a patterned and cured inorganic antireflective coating (ARC)that is located atop a substrate, said inorganic ARC comprises a curedpolymer that has at least one monomer unit comprising the formula M-R¹wherein M is at least one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and Laand R¹ is a chromophore, and said at least one cured and patterned low-kmaterial and said patterned and cured inorganic antireflective coating(ARC) having conductively filled regions embedded therein.

In some embodiments of this method of the present invention, M withinthe monomer unit may also be bonded to organic ligands including atomsof C and H, a cross-linking component, another chromophore or mixturesthereof. The organic ligands may further include one of O, N, S and F.When the organic ligand is bonded to M, it is bonded to M through C, O,N, S, or F.

In other embodiments of the present invention, the ARC may also includeat least one second monomer unit, in addition to the at least onemonomer unit represented by the formula M-R¹. When present, the at leastone second monomer unit has the formula M′-R², wherein M′ is at leastone of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La, and R² is across-linking agent. M and M′ may be the same or different elements. Inthese two formulae, M and M′ within the monomer unit may be also bebonded to organic ligands including atoms of C and H, a cross-linkingcomponent, a chromophore or mixtures thereof. The organic ligands mayfurther include one of O, N, S and F. When the organic ligand is bondedto M and M′, it is bonded to M or M′ through C, O, N, S, or F.

The liquid ARC composition comprising M-R¹ or M-R¹ and M′-R² may alsocomprise at least one additional component, including a separatecrosslinker, an acid generator or a solvent.

In some further embodiments of the present invention, a dual-damasceneinterconnect structure including first and second cured and patternedlow-k materials is provided. In yet another embodiment of the presentinvention, a single-damascene interconnect structure is provided.

In a further embodiment of the present invention a patterned dielectriccap layer is located beneath the inorganic antireflective coating. Instill another embodiment of the present invention, another dielectriccap can be present atop the patterned low-k film.

In yet another embodiment of the present invention, the conductivelyfilled regions comprise Al, Cu or a Cu alloy. In an even furtherembodiment of the present invention, the conductively filled regionscomprise a single via, a single line, a combined via/line or a combinedline/via.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1F are pictorial representations (through cross sectionalviews) depicting the basic processing steps employed for fabricating adual-damascene interconnect structure using patternable dielectrics ason-chip electrical insulators on a semiconductor chip.

FIG. 2 shows the interconnect structure that is formed after furtherprocessing of the structure shown in FIG. 1F.

FIGS. 3A-3D are pictorial representations (through cross sectionalviews) depicting the basic processing steps employed for fabricating asingle-damascene interconnect structure using a patternable dielectricas an on-chip electrical insulator on a semiconductor chip.

FIG. 4 shows the interconnect structure that is formed after furtherprocessing of the structure shown in FIG. 3D.

DETAILED DESCRIPTION OF THE INVENTION

The present invention, which provides single-damascene or dual-damascenelow-k interconnect structures with a combined inorganic antireflectivecoating (ARC) and patternable low-k dielectric and methods offabricating such interconnect structures, will now be described ingreater detail by referring to the following discussion and drawingsthat accompany the present application. It is noted that the drawingsthat accompany the present application are provided for illustrativepurposes only, and, as such, these drawings are not drawn to scale.

In the following description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps and techniques, in order to provide a thoroughunderstanding of the present invention. However, it will be appreciatedby one of ordinary skill in the art that the invention may be practicedwithout these specific details. In other instances, well-knownstructures or processing steps have not been described in detail inorder to avoid obscuring the invention.

It will be understood that when an element as a layer, region orsubstrate is referred to as being “on” or “over” another element, it canbe directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present. When the word “conductive” or“conducting” is used, it is used to mean electrically conductive orelectrically conducting.

As stated above, this invention circumvents the prior art drawbacks ofcurrent integration by combining the functions of a photoresist and adielectric material into one material. This one material, called apatternable low-k dielectric herein, acts as a photoresist during thelithographic patterning process and, as such a separate photoresist isnot required or used in the present invention. After lithographicpatterning, the patternable low-k dielectric is subsequently convertedinto a low-k material during a post patterning cure. In this way, theinventive method avoids plasma etching and the complex sacrificial filmstack and processes required for patterning. Specifically, thisinvention relates to a simplified method of fabricating single-damasceneand dual-damascene low-k interconnect structures with at least onepatternable dielectric.

In general terms, a method is provided that comprises depositing atleast one patternable low-k material on a surface of an inorganicantireflective coating (ARC) that is located atop a substrate, saidinorganic ARC is liquid deposited and comprises a polymer that has atleast one monomer unit comprising the formula M-R¹ wherein M is at leastone of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La and R¹ is a chromophore;forming at least one interconnect pattern within said at least onepatternable low-k material, said at least one interconnect pattern isformed without utilizing a separate photoresist material; and curing theat least one patternable low-k material as well as the ARC. Theinventive method can be used to form dual-damascene interconnectstructures as well as single-damascene interconnect structures.

In other embodiments of the present invention, the ARC may also includeat least one second monomer unit, in addition to the at least onemonomer unit represented by the formula M-R¹. When present, the at leastone second monomer unit has the formula M′-R², wherein M′ is at leastone of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La, and R² is across-linking agent. M and M′ may be the same or different elements. Inthese two formulae, M and M′ within the monomer unit may be also bebonded to organic ligands including atoms of C and H, a cross-linkingcomponent, a chromophore or mixtures thereof. The organic ligands mayfurther include one of O, N, S and F. When the organic ligand is bondedto M and M′, it is bonded to M or M′ through C, O, N, S, or F.

The liquid ARC composition comprising M-R¹ or M-R¹ and M′-R² may alsocomprise at least one additional component, including a separatecrosslinker, an acid generator or a solvent.

The present invention will now be described in reference to FIGS. 1A-1Fwhich illustrate an embodiment of the present invention in which adual-damascene structure using patternable dielectrics as on-chipelectrical insulators on a semiconductor chip is provided.

FIG. 1A illustrates an initial structure 10 that is utilized in thisembodiment of the present invention. The initial structure 10 includes asubstrate 12, an optional dielectric cap 14 located on a surface ofsubstrate 12, and inorganic antireflective coating 16 located on asurface of the optional dielectric cap 14.

The substrate 12 may comprise a semiconducting material, an insulatingmaterial, a conductive material or any combination thereof (e.g., alower level of an interconnect structure). When the substrate 12 iscomprised of a semiconducting material, any semiconductor such as Si,SiGe, SiGeC, SiC, Ge alloys, GaAs, InAs, InP and other III/V or II/VIcompound semiconductors and organic semiconductors may be used. Inaddition to these listed types of semiconducting materials, the presentinvention also contemplates cases in which the semiconductor substrateis a layered semiconductor such as, for example, Si/SiGe, Si/SiC,silicon-on-insulators (SOIs) or silicon germanium-on-insulators (SGOIs).

When the substrate 12 is an insulating material, the insulating materialcan be an organic insulator, an inorganic insulator or a combinationthereof including multilayers. The substrate 12 may also include apatternable low-k dielectric material of this invention as well. Whenthe substrate 12 is a conducting material, the substrate may include,for example, polySi, an elemental metal, alloys of elemental metals, ametallic silicide, a metallic nitride, conductive nanotubes or nanowiresor combinations thereof including multilayers. When the substrate 12comprises a semiconducting material, one or more semiconductor devicessuch as, for example, complementary metal oxide semiconductor (CMOS)devices can be fabricated thereon.

The optional dielectric cap 14 is formed on the surface of substrate 12utilizing a conventional deposition process such as, for example,chemical vapor deposition (CYD), plasma enhanced chemical vapordeposition (PECVD), atomic layer deposition (ALD), chemical solutiondeposition, spin coating, brush coating, spray coating, dip coating, orevaporation. The dielectric cap 14 comprises any suitable dielectriccapping material such as, for example, SiC, SiN, SiO₂, a carbon dopedoxide, a nitrogen and hydrogen doped silicon carbide SiC(N,H) ormultilayers thereof. This dielectric cap can be a continuous layer or adiscontinuous layer. It can also be a select cap, such as CoWP, on topof the metal area only. The thickness of the dielectric cap 14 may varydepending on the technique used to form the same as well as the materialmake-up of the layer. Typically, the dielectric cap 14 has a thicknessfrom about 15 to about 55 nm, with a thickness from about 25 to about 45nm being more typical.

Next, an inorganic antireflective coating (ARC) 16 is formed on asurface of the optional dielectric cap 14 if present, or directly on asurface of the substrate 12 when the dielectric cap 14 is not present.The ARC 16 may be designed to control reflection of light that istransmitted through the patternable low-k film (to be subsequentlyformed), reflected off the substrate and back into the patternable low-kfilm, where it can interfere with incoming light and cause the low-kfilm to be unevenly exposed. The ARC's optical constants are definedhere as the index of refraction n and the extinction coefficient k. Ingeneral, ARC 16 can be modeled so as to find optimum optical parameters(n and k values) of ARC as well as optimum thickness. The preferredoptical constants of the ARC 16 are in the range from about n=1.4 ton=2.6 and k=0.01 to k=0.78 at a wavelength of 248, 193 and 157, 126 nmand extreme ultraviolet (13.4 nm) radiation.

The optical properties and thickness of ARC 16 is optimized to obtainoptimal resolution and profile control of the patternable low-k materialduring the subsequent patterning steps, which is well known to thoseordinarily skilled in the art. The thickness of the ARC 16 may varydepending on the technique used to form the same as well as the materialmake-up of the layer. Typically, the ARC 16 has a thickness from about 5to about 200 nm, with a thickness from about 20 to about 140 nm beingmore typical.

The ARC 16 of the present invention is formed by a liquid depositionprocess including for example, spin-on coating, spray coating, dipcoating, brush coating, evaporation or chemical solution deposition. TheARC 16 comprises a polymer that has at least one monomer unit comprisingthe formula M-R¹ wherein M is at least one of Si, Ge, B, Sn, Fe, Ta, Ti,Ni, Hf and La and R¹ is a chromophore. In some embodiments, M within themonomer unit may also be bonded to organic ligands including atoms of Cand H, a cross-linking component, another chromophore or mixturesthereof. The organic ligands may further include one of O, N, S and F.When the organic ligand is bonded to M, it is bonded to M through C, O,N, S, or F.

In other embodiments of the present invention, the ARC may also includeat least one second monomer unit, in addition to the at least onemonomer unit represented by the formula M-R¹. When present, the at leastone second monomer unit has the formula M′-R², wherein M′ is at leastone of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La, and R² is across-linking agent. M and M′ may be the same or different elements. Inthese two formulae, M and M′ within the monomer unit may be also bebonded to organic ligands including atoms of C and H, a cross-linkingcomponent, a chromophore or mixtures thereof. The organic ligands mayfurther include one of O, N, S and F. When the organic ligand is bondedto M and M′, it is bonded to M or M′ through C, O, N, S, or F.

The liquid ARC composition comprising M-R¹ or M-R¹ and M′-R² may alsocomprise at least one additional component, including a separatecrosslinker, an acid generator or a solvent.

The ARC 16 is formed by liquid phase deposition of a liquid compositionthat includes an inorganic precursor that includes atoms of M, C and H,wherein M is at least one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La.The inorganic precursor used in forming the ARC may optionally includeatoms of O, N, S, F or mixtures thereof. In some embodiments, M ispreferably Si. The liquid composition also includes, in addition to theinorganic precursor, a chromophore, a cross-linking component and anacid generator.

One embodiment of the inventive inorganic ARC composition comprises M-R¹and M′-R² units, wherein M and M′ is at least one of Si, Ge, B, Sn, Fe,Ta, Ti, Ni, Hf and La or is selected from Group IIIB to Group VIB, GroupIIIA, Group IVA. The inorganic precursor used in forming the ARC mayoptionally include atoms of O, N, S, F or mixtures thereof. Oneembodiment of inventive inorganic ARC composition comprises the MO_(y)unit which can be any one of many different metal-oxide forms. Anexemplary list of such metal-oxide forms for a particular metal is asfollows:

MO₃; wherein M is Sc, Y, lanthanide, and Group IIIA; B, Al, Ga or In.

MO₄; wherein M is Group IVB; Ti, Zr or Hf and Group IVA; Sn or Ge.

MO₅; wherein M is Group VB; V, Nb or Ta; or P. The Group VB metals arealso known to form stable metal oxo forms, LMO3, wherein L is an oxo.

LMO; many of the listed metals form stable acetoacetato-metal complexes.

LMO; many of the listed metals form stable cyclopentadienyl-metalcomplexes.

LMO; wherein L is an alkoxy ligand; M is Sc, Y, or lanthanide, GroupIVB, and Group VB.

LMO; wherein L is an alkyl or phenyl ligand; M is Group IIIA or GroupIVA.

The chromophore, cross-linking component and acid generator that can beused in the present invention are defined in greater detail with respectto the following preferred embodiment of the present invention.

In a preferred embodiment, the ARC 16 is characterized by the presenceof an SiO-containing polymer having pendant chromophore moieties. Thepolymer containing SiO moieties may be a polymer containing SiO moietiesin the polymer backbone and/or in pendant groups. Preferably, thepolymer contains SiO moieties in its backbone. The polymer is preferablya siloxane, a silane, a carbosilane, an oxycarbosilane, anorganosilicate, a silsesquioxane, or an organosiloxane, more preferablyorganosilsesquioxane. The polymer should have solution and film-formingcharacteristics conducive to forming a layer by conventionalspin-coating. In addition to the chromophore moieties discussed below,the SiO-containing polymer also preferably contains a plurality ofreactive sites distributed along the polymer for reaction with thecross-linking component.

Examples of suitable polymers include polymers having the silsesquioxane(ladder or network) structure. Such polymers preferably contain monomershaving structures (I) and (II) below:

where R₁ comprises a chromophore and R₂ comprises a reactive site forreaction with the cross-linking component.

Alternatively, general linear organosiloxane polymers containingmonomers (III) and (IV) can be used:

where R₁ and R₂ are as described above. In some cases, the polymercontains various combinations of monomers (I)-(IV) such that the averagestructure for R₁-containing monomers may be represented as structure (V)below and the average structure for R₂-containing monomers may berepresented by structure (VI) below:

where x is from about 1 to about 1.5. In theory, x may be greater than1.5, however, such composition generally do not possess characteristicssuitable for spin-coating processes (e.g., they form undesirable gel orprecipitate phases).

Generally, silsesquioxane polymers are preferred. If the ordinaryorganosiloxane polymers are used (e.g., monomers of structures (III) and(IV)), then preferably, the degree of cross-linking is increasedcompared to formulations based on silsesquioxanes.

The chromophore-containing groups R₁ (or R¹ in the generic descriptionabove) may contain any suitable chromophore which (i) can be graftedonto the SiO-containing polymer (or M moiety of the generic monomerdefined above) (ii) has suitable radiation absorption characteristics atthe imaging wavelength, and (iii) does not adversely affect theperformance of the layer or any overlying layers.

Preferred chromophore moieties include benzene and its derivatives,chrysenes, pyrenes, fluoranthrenes, anthrones, benzophenones,thioxanthones, and anthracenes. Anthracene derivatives, such as thosedescribed in U.S. Pat. No. 4,371,605 may also be used; the disclosure ofthis patent is incorporated herein by reference. In one embodiment,phenol, hydroxystyrene, and 9-anthracene methanol are preferredchromophores. The chromophore moiety preferably does not containnitrogen, except for possibly deactivated amino nitrogen such as inphenol thiazine.

The chromophore moieties may be chemically attached by acid-catalyzedO-alkylation or C-alkylation such as by Friedel-Crafts alkylation. Thechromophore moieties may also be chemically attached by hydrosilylationof SiH bond on the parent polymer. Alternatively, the chromophore moietymay be attached by an esterification mechanism. A preferred acid forFriedel-Crafts catalysis is HCl.

Preferably, about 15 to about 40% of the functional groups containchromophore moieties. In some instances, it may be possible to bond thechromophore to the monomer before formation of the SiO-containingpolymer. The site for attachment of the chromophore is preferably anaromatic group such as a hydroxybenzyl or hydroxymethylbenzyl group.Alternatively, the chromophore may be attached by reaction with othermoieties such as cyclohexanol or other alcohols. The reaction to attachthe chromophore is preferably an esterification of the alcoholic OHgroup.

R₂ (or R² in the generic description above) comprises a reactive sitefor reaction with the cross-linking component. Preferred reactivemoieties contained in R₂ are alcohols, more preferably aromatic alcohols(e.g., hydroxybenzyl, phenol, hydroxymethylbenzyl, etc.) orcycloaliphatic alcohols (e.g., cyclohexanoyl). Alternatively, non-cyclicalcohols such as fluorocarbon alcohols, aliphatic alcohols, aminogroups, vinyl ethers, and epoxides may be used.

Preferably, the SiO-containing polymer (before attachment of thechromophore) is poly(4-hydroxybenzylsilsesquioxane), Examples of othersilsesquioxane polymers of the invention include:poly(p-hydroxyphenylethylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-p-hydroxy-alpha-methylbenzylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-methoxybenzylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-t-butylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-cyclohexylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-phenylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-bicycloheptylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-hydroxybenzylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-methoxybenzylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-t-butylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-cyclohexylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-phenylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-bicycloheptylsilsesquioxane),poly(p-hydroxybenzylsilsesquioxane-co-p-hydroxyphenylethylsilsesquioxane),andpoly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-alpha-methylbenzylsilsesquioxane).

The SiO-containing polymers of the invention preferably have a weightaverage molecular weight, before reaction with the cross-linkingcomponent, of at least about 1000, more preferably a weight averagemolecular weight of about 1000-10000.

The cross-linking component is preferably a crosslinker that can bereacted with the SiO containing polymer in a manner which is catalyzedby generated acid and/or by heating. Generally, the cross-linkingcomponent used in the antireflective compositions of the invention maybe any suitable cross-linking agent known in the negative photoresistart which is otherwise compatible with the other selected components ofthe composition. The cross-linking agents preferably act to crosslinkthe polymer component in the presence of a generated acid. Preferredcross-linking agents are glycoluril compounds such as tetramethoxymethylglycoluril, methylpropyltetramethoxymethyl glycoluril, andmethylphenyltetramethoxymethyl glycoluril, available under thePOWDERLINK trademark from American Cyanamid Company. Other possiblecross-linking agents include: 2,6-bis(hydroxymethyl)-p-cresol, compoundshaving the following structures:

including their analogs and derivatives, such as those found in JapaneseLaid-Open Patent Application (Kokai) No. 1-293339, as well as etherifiedamino resins, for example methylated or butylated melamine resins(N-methoxymethyl- or N-butoxymethyl-melamine respectively) ormethylated/butylated glycolurils, for example as can be found inCanadian Patent No. 1 204 547. Other cross-linking agents such asbis-epoxies or bis-phenols (e.g., bisphenol-A) may also be used.Combinations of cross-linking agents may be used.

The acid generator is preferably an acid generator compound thatliberates acid upon thermal treatment. A variety of known thermal acidgenerators are suitably employed such as, for example,2,4,4,6-tetrabromocyclohexadienone, benzoin tosylate, 2-nitrobenzyltosylate and other alkyl esters of organic sulfonic acids, blocked alkylphosphoric acids, blocked perfluoroalkyl sulfonic acids, alkylphosphoric acid/amine complexes, perfluoroalkyl acid quats wherein theblocking can be by covalent bonds, amine and quaternary ammonium.Compounds that generate a sulfonic acid upon activation are generallysuitable. Other suitable thermally activated acid generators aredescribed in U.S. Pat. Nos. 5,886,102 and 5,939,236; the disclosures ofthese two patents are incorporated herein by reference. If desired, aradiation-sensitive acid generator may be employed as an alternative toa thermally activated acid generator or in combination with a thermallyactivated acid generator. Examples of suitable radiation-sensitive acidgenerators are described in U.S. Pat. Nos. 5,886,102 and 5,939,236.Other radiation-sensitive acid generators known in the resist art mayalso be used as long as they are compatible with the other components ofthe antireflective composition. Where a radiation-sensitive acidgenerator is used, the cure (cross-linking) temperature of thecomposition may be reduced by application of appropriate radiation toinduce acid generation which in turn catalyzes the cross-linkingreaction. Even if a radiation-sensitive acid generator is used, it ispreferred to thermally treat the composition to accelerate thecross-linking process (e.g., for wafers in a production line).

The antireflective compositions of the invention preferably contain (ona solids basis) (i) from about 50 to about 98 wt. % of a polymerincluding M, more preferably from about 70 to about 80 wt. %, (ii) fromabout 1 to about 50 wt. % of cross-linking component, more preferablyfrom about 3 to about 25%, most preferably about from about 5 to about25 wt. %, and (iii) from about 1 to about 20 wt. % acid generator, morepreferably about 1-15 wt. %.

The ARC 16 of the present invention is formed by a liquid depositionprocess including for example, spin-on coating, spray coating, dipcoating, brush coating, evaporation or chemical solution deposition.After applying the ARC 16, a post deposition baking step is typically,but not necessarily always, required to remove unwanted components, suchas solvent, and to effect crosslinking. When performed, the baking stepis conducted at a temperature from about 60° to about 400° C., with abaking temperature from about 80° to about 300° C. being even morepreferred. The duration of the baking step varies and is not critical tothe practice of the present invention. The as-deposited ARC 16 mayfurther undergo a curing process. The curing is performed in the presentinvention by a thermal cure, an electron beam cure, an ultra-violet (UV)cure, an ion beam cure, a plasma cure, a microwave cure or anycombination thereof.

In addition, the composition of the starting precursor as well as theintroduction of oxygen, nitrogen, fluorine containing precursors alsoallows the tunability of these films. The ARC's optical constants aredefined here as the index of refraction n and the extinction coefficientk. In general, ARC 16 can be modeled so as to find optimum opticalparameters (n and k values) of ARC as well as optimum thickness. Asmentioned above, the preferred optical constants of the ARC 15 are inthe range from about n=1.4 to n=2.6 and k=0.01 to k=0.78 at a wavelengthof 248, 193 and 157, 126 nm and extreme ultraviolet (13.4 μm) radiation.

In addition to the above, the ARC 16 does not interact with thepatternable low-k material to induce residue, footing or undercutting.Moreover, the ARC 16 has good etch selectivity to the patternabledielectric material. Etch selectivities of 1.5-4 to 1 of the ARC tolow-k dielectric material can be obtained. Furthermore, the use of theARC 16 of the present invention maintains the pattern and structuralintegrity after curing of the patternable low-k material. This iscritical as the ARC layer 16 is retained as a permanent part of thefinal interconnect stack. Another beneficial attribute of the inventiveARC is that it has a relative dielectric constant that is less than 7.0.

Next, and as illustrated in FIG. 1B, a first patternable low-k material18, which combines the function of a photoresist and low-k material intoone single material is provided. As shown, the first patternable low-kmaterial 18 is provided directly on the surface of the ARC 16.

The first patternable low-k material 18 is provided (i.e., formed)utilizing a conventional deposition process including, for example,spin-on-coating, spray coating, dip coating, brush coating, evaporation.After applying the first patternable low-k material 18, a postdeposition baking step is typically, but not necessarily always,required to remove unwanted components, such as solvent. When performed,the baking step is conducted at a temperature from about 60° to about200° C., with a baking temperature from about 80° to about 160° C. beingeven more preferred. The duration of the baking step varies and is notcritical to the practice of the present invention.

The thickness of the first patternable low-k material 18 may varydepending on the technique used to form the same as well as the materialmake-up of the layer. Typically, the first patternable low-k material 18has a thickness from about 10 to about 10000 nm, with a thickness fromabout 50 to about 2000 nm being more typical.

As stated above, the first patternable low-k material 18 functions as aphotoresist and is converted into a low-k material during postpatterning processing, UV light, electron beam, ion beam, microwave,plasma cure, thermal cure or combinations thereof. For instance, thefirst patternable low-k material 18 may comprise a functionalizedpolymer having one or more acid-sensitive imageable groups. Thesepolymers or blends of polymers can be converted into low-k materialsafter subsequent processing.

More specifically, the first patternable low-k material 18 comprisesphoto/acid-sensitive polymers of hydrocarbons, fluorinated hydrocarbons,siloxane, silane, carbosilane, oxycarbosilane, organosilicates,silsesquioxanes and the like. The polymers include, for example,silsesquioxane-type polymers including caged, linear, branched orcombinations thereof. In one embodiment, the first patternabledielectric material 18 comprises a blend of these photo/acid-sensitivepolymers. The first patternable dielectric material 18 may furthercomprises at least one sacrificial pore generator to reduce thedielectric constant in its cured form. Examples of patternabledielectric materials useable with the present disclosure are disclosedin U.S. Pat. Nos. 7,041,748, 7,056,840, and 6,087,064, all of which areincorporated herein by reference in their entirety. The dielectricconstant of the patternable low-k material 18 after cure is generally nomore than 4.3. The dielectric constant may be greater than 1 and up toabout 4.3, more preferably from about 1 to about 3.6, even morepreferably from about 1 to about 3.0, further more preferably from about1 to about 2.5, with from about 1 to about 2.0 being most preferred.

The first patternable low-k material 18 is formed from a compositionthat includes one of the above mentioned polymers or polymer blends, aphotoacid generator, a base additive and a solvent typically used in aphotoresist. The photoacid generators, base additives and solvents arewell known to those skilled in the art and, as such, details regardingthose components are not fully provided.

In a preferred embodiment, the first patternable low-k material 18 is anegative-tone patternable low-k material comprising a silsesquioxanepolymer or copolymer including, for example, poly(methylsilsesquioxane)(PMS), poly(p-hydroxybenzylsilsesquioxane) (PHBS),poly(p-hydroxyphenylethylsilsesquioxane) (PHPES),poly(p-hydroxyphenylethylsilsesquioxane-co-p-hydroxy-alpha-methylbenzylsilsesquioxane) (PHPE/HMBS),poly(p-hydroxyphenylethylsilsesquioxane-co-methoxybenzylsilsesquioxane)(PHPE/MBS),poly(p-hydroxyphenylethylsilsesquioxane-co-t-butylsilsesquioxane)(PHPE/BS),poly(p-hydroxyphenylethylsilsesquioxane-co-cyclohexylsilsesquioxane)(PHPE/CHS),poly(p-hydroxyphenylethylsilsesquioxane-co-phenylsilsesquioxane)(PHPE/PS),poly(p-hydroxyphenylethylsilsesquioxane-co-bicycloheptylsilsesquioxane)(PHPE/BHS), polyp-hydroxy-alpha-methylbenzylsilsesquioxane) (PHMBS),polyp-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-hydroxybenzylsilsesquioxane)(PHMB/HBS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-methoxybenzylsilsesquioxane)(PHIMB/MBS),poly(p-hydroxy-alplha-methylbenzylsilsesquioxane-co-t-butylsilsesquioxane)(PHMB/BS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-cyclohexylsilsesquioxane)(PHMB/CHS),poly(p-hydroxy-alpha-metylbenzylsilsesquioxane-co-phenylsilsesquioxane)(PHMB/PS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-bicycloheptylsilsesquioxane)(PHMB/BHS),poly(p-hydroxybenzylsilsesquioxane-co-p-hydroxyphenzylethylsilsesquioxane)(PHB/HPES), and poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-alpha-methyl-benzylsilsesquioxane)(PHMB/MBS).

In the compositions containing a blended polymer component, thesilsesquioxane polymer in the blend may be selected from thesilsesquioxane polymers described above or may be selected from othersilsesquioxane polymers such as, for example, poly(methylsilsesquioxane)(PMS), poly(p-hydroxybenzylsilsesquioxane) (PHBS),poly(p-hydroxybenzylsilsesquioxane-co-methoxybenzylsilsesquioxane)(PHB/MBS),polyp-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-alpha-methybenzylsilsesquioxane)(PHMB/MBS), poly(p-hydroxybenzylsilsesquioxane-co-t-butylsilsesquioxane)(PHB/BS),poly(p-hydroxybenzylsilsesquioxane-co-cyclohexylsilsesquioxane)(PHB/CHS), poly(p-hydrooxybenzylsilsesquioxane-co-phenylsilsesquioxane)(PHB/PS),poly(p-hydroxybenzylsilsesquioxane-co-bicycloheptylsilsesquioxane)(PHB/BHS), and caged silsesquioxanes such as octakis(glycidyloxypropyl)dimethylsilyloxy)silsesquioxane, octakis[cyclohexenyl epoxide)dimethylsilyloxy]silsesquioxane, octakis[4-(hydroxyphenylethyl)dimethylsilyloxy]silsesquioxane, andoctakis[{2-(1′,1′-bis(trifluoromethyl)-1′-hydroxyethyl)norbornyl}dimethylsilyloxy]silsesquioxane.If desired, a combination of different silsesquioxane polymers may beused in the blend with the non-silsesquioxane polymer.

For positive tone patternable low-k material, the silicon-containingpolymer employed in the present invention may be a homopolymer or acopolymer. Suitable types of such silicon-containing polymers includehomopolymers or copolymers containing at least one monomer selected fromthe group consisting of a siloxane, a silane, a silsesquioxane and asilyne. Highly preferred silicon-backbone polymers are selected from thegroup consisting of poly(hydroxyphenyl alkyl)silsesquioxanes and poly(hydroxyphenyl alkyl) siloxanes, wherein the alkyl is a C₁₋₃₀ moiety.These preferred silicon-containing polymers are preferably fully orpartially protected with acid-sensitive protecting groups.

The positive-tone patternable low-k material may comprise blends of anon-silicon containing polymer and a silicon-containing polymericadditive with a silicon-containing substituent bonded to the polymericbackbone, the silicon-containing polymeric additive may be a homopolymeror copolymer containing at least one monomer having a silicon-containingsubstituent. The silicon-containing substituent may or may not be acidsensitive. Typically, however the substituent is acid sensitive whencontaining a C₂ alkyl moiety. Preferably, the silicon-containingsubstituent is attached to a monomer selected from the group consistingof hydroxystyrene, an acrylate, a methacrylate, an acrylamide, amethacrylamide, itaconate an itaconic half ester or a cycloolefin.Preferred silicon-containing substituents include: siloxane, silane andcubic silsesquioxanes. The silicon-containing polymer may furtherinclude silicon-free monomers such as those selected from the groupconsisting of styrene, hydroxystyrene, acrylic acid, methacrylic acid,itaconic acid and an anhydride such as maleic anhydride and itaconicanhydride.

Preferred monomers containing silicon-containing substituents aretrimethylsilyl alkyl acrylate, trimethylsilyl alkyl methacrylate,trimethylsilyl alkyl itaconate, tris(trimethylsilyl)silyl alkyl acrylatetris(trimethylsilyl)silyl alkyl methacrylate, tris(trimethylsilyl)silylalkyl itaconate, tris(trimethylsilyloxy)silyl alkyl acrylate,tris(trimethylsilyloxy)silyl alkyl methacrylate,tris(trimethylsilyloxy)silyl alkyl itaconate, alkylsilyl styrene,trimethylsilylmethyl(dimethoxy)silyloxy alkyl acrylate,trimethylsilylmethyl(dimethoxy)silyloxy alkyl methacrylate,trimethylsilylmethyl(dimethoxy)silyloxy alkyl itaconate, trimethylsilylalkyl norbornene-5-carboxylate alkyl, tris(trimethylsilyl(silyl alkylnorbornene-5-carboxylate and tris(trimethylsilyloxy)silyl alkylnorbornene-5-carboxylate, wherein alkyl is a C₁₋₅ moiety.

Highly preferred species of these monomers are3-(3,5,7,9,11,13,15-heptacyclopentylpentacyclo[9.5.1.13,9.15,15.17,13]-octasiloxan-1-yl)propylmethacrylate,1,3,5,7,9,11,13-heptacyclopentyl-15-vinylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane,methacrylamidotrimethylsilane,O-(methacryloxyethyl)-N-(triethoxysilylpropyl)urethane,methacryloxyethoxytrimethylsilane,N-(3-methacryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane,(methacryloxymethyl)bis(trimethylsiloxy)methylsilane,(m,p-vinylbenzyloxy)trimethylsilane,methacryloxypropyltris(trimethylsiloxy)silane,methacryloxytrimethylsilane,3-methacryloxypropylbis(trimethylsiloxy)methylsilane,3-methacryloxypropyldimethylchlorosilane,methacryloxypropyldimethylethoxysilane,methacryloxypropyldimethylmethoxysilane,methacryloxypropylheptacyclopentyl-T8-silsequioxane,methacryloxypropylmethyldichlorosilane,methacryloxypropylmethyldiethoxysilane,methacryloxypropylmethyldimethoxysilane,(methacryloxymethyl)dimethylethoxysilane,(methacryloxymethyl)phenyldimethylsilane(phenyldimethylsilyl)methylmethaerylate,methacryloxymethyltriethoxysilane, methacryloxymethyltrimethoxysilane,methacryloxymethyltris(trimethylsiloxy)silane,O-methacryloxy(polyethyleneoxy)trimethylsilane,methacryloxypropylpentamethyldisiloxane, methacryloxypropylsilatrane,methacryloxypropylsiloxane macromer, methacryloxypropyl terminatedpolydimethylsiloxane, methacryloxypropyltrichlorosilane,methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane,methacryloxypropyltris(methoxyethoxy)silane,p-(t-butyldimethylsiloxy)styrene, butenyltriethoxysilane,3-butenyltrimethylsilane, (3-acryloxypropyl)trimethoxysilane,(3-acryloxypropyl)tris(trimethylsiloxy)silane,O-(trimethylsilyl)acrylate, 2-trimethylsiloxyethlacrylate,N-(3-acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane,(3-acryloxypropyl)dimethylmethoxysilane,(3-acryloxypropyl)methylbis(trimethylsiloxy)silane,(3-acryloxypropyl)methyldichlorosilane, and(3-acryloxypropyl)methyldimethoxysilane,(3-acryloxypropyl)trichlorosilane.

The extent of protection and the amount of co-monomer present in thesilicon containing polymeric additive are such that the patternablelow-k material resist composition will provide good lithographyperformance, i.e., high resolution and good process window Examples ofprotecting groups which can be employed are cyclic and branched(secondary and tertiary) aliphatic carbonyls, esters or etherscontaining from 3 to 30 carbon atoms, acetals, ketals and aliphaticsilylethers.

Examples of cyclic or branched aliphatic carbonyls that may be employedin the present invention include, but are not limited to phenoliccarbonates; t-alkoxycarbonyloxys such as t-butoxylcarbonyloxy andisopropyloxycarbonyloxy. A highly preferred carbonate ist-butoxylcarbonyloxy.

Some examples of cyclic and branched ethers that may be employed in thepresent invention include, but are not limited to: benzyl ether andt-alkyl ethers such t-butyl ether. Of the aforesaid ethers, it is highlypreferred to use t-butyl ether.

Examples of cyclic and branched esters that can be employed in thepresent invention are carboxylic esters having a cyclic or branchedaliphatic substituent such as t-butyl ester, isobornyl ester,2-methyl-2-admantyl ester, benzyl ester, 3-oxocyclohexanyl ester,dimethylpropylmethyl ester, mevalonic lactonyl ester,3-hydroxy-g-butyrolactonyl ester, 3-methyl-g-butylrolactonyl ester,bis(trimethylsilyl)isopropyl ester, trimethylsilylethyl ester,tris(trimethylsilyl)silylethyl ester and cumyl ester.

Some examples of acetals and ketals that can be employed in the presentinvention include, but are not limited to: phenolic acetals and ketalsas well as tetrahydrofuranyl, tetrahydropyranyl, 2-ethoxyethyl,methoxycyclohexanyl, methoxycyclopentanyl, cyclohexanyloxyethyl,ethoxycyclopentanyl, ethoxycyclohexanyl, methoxycycloheptanyl andethoxycycloheptanyl. Of these, it is preferred that amethoxycyclohexanyl ketal be employed,

Illustrative examples of silylethers that can be employed in the presentinvention include, but are not limited to: trimethylsilylether,dimethylethylsilylether and dimethylpropylsilylether. Of thesesilylethers, it is preferred that trimethylsilylether be employed.

In a preferred embodiment for negative-tone patternable low-k materialsof the present invention are two miscible, or compatible,silsesquioxanes. The first silsesquioxane polymer is a linear, branched,caged compound or combination thereof having the following structuralformula:

wherein each occurrence of R₁ is one or more acidic functional groupsfor base solubility; each occurrence of R₂ is a carbon functionality forcontrolling polymer dissolution in an aqueous base; R₁ is not equal toR₂; m and n represent the number of repeating units; m is an integer;and n is zero or an integer greater than zero.

In the present invention, R₁ is not limited to any specific functionalgroup, and is preferably selected from among linear or branched alkylswhich are substituted with OH, C(O)OH, and/or F; cycloalkyls which aresubstituted with OH, C(O)OH, and/or F; aromatics which are substitutedwith OH, C(O)OH, and/or F; arenes that are substituted with OH, C(O)OH,and/or F; and acrylics which are substituted with OH, C(O)OH, and/or F.Examples of preferred R₁ include:

In the present invention, R₂ is not limited to any specific carbonfunctional group, and is preferably selected from among linear orbranched alkyls, cylcoalkyls, aromatics, arenes, and acrylates.

The silsesquioxane polymers of the present invention have a weightaveraged molecular weight of about 400 to about 500,000, and morepreferable from about 1500 to about 10,000. The R₁ and R₂ proportionsand structures are selected to provide a material suitable forphotolithographic processes and maintaining pattern fidelity after postpatterning cure.

A second polymer component of the blend material includes but is notlimited to a family of organosilicates known as silsesquioxanes, havingthe structural formula:

wherein R₃ is preferable selected from alkyls, cycloalkyls, aryl, or acombination thereof and are commercially available from Dow Corning,Shin-Etsu, or JSR, for example. The silsesquioxane is preferablypoly(methylsilsesquioxane), and n is an integer about 10 to about 1,000or more (including copolymers). The silsesquioxane polymers possesssilanol end groups, but may also include halosilanes, acetoxysilanes,silylamines, and alkoxysilanes. In a preferred embodiment of the presentinvention, silsesquioxane polymers, LKD-2021 or LKD-2056 (from JSRCorporation) which contain silanol end groups are employed.

A third component of the present invention is a photosensitive acidgenerator (PAG) that is compatible with the other components. Examplesof preferred PAGs include:-(trifluoro-methylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide(MDT), onium salts, aromatic diazonium salts, sulfonium salts,diaryliodonium salts, and sulfonic acid esters of N-hydroxyamides or-imides, as disclosed in U.S. Pat. No. 4,371,605. The content of the'605 patent is incorporated herein by reference. A weaker acid generatedfrom a PAG such as N-hydroxy-naphthalimide (DDSN) may be used.Combinations of PAGs may be used.

The composition of the silsesquioxane polymers in the blend formulationis 1 to 99% of the total polymer composition. In the preferredembodiment of the invention, the composition of the acid sensitivepolymer is 20 to 80% of the total polymer composition, and even morepreferred, 30 to 60%.

A third component of the patternable low-k composition of the presentinvention is a pore-generating compound, called a porogen. The porogenprovides nanoscopic pores in the composition of matter of the presentinvention which further reduces the dielectric constant of the material.

The porogen that can be used in the present invention includes miscibleor phase separated, i.e., non-miscible, polymers that are capable ofdecomposing under heat or radiation. Alternatively, the porogen may beextracted with supercritical fluid techniques. Examples of porogens thatmay be employed in the present invention include: homopolymers,copolymers, organic nanoscopic polymers, thermoplastic polymers,star-shaped polymers, dendrimers or crosslinked polymers that remainsubstantially dormant during the patterning process. After patterning,the pore generating polymers are decomposed or extracted to enhance thedielectric properties of the material of the present invention withoutseverely degrading the pattern fidelity. The decomposition of theporogen may be by heat or radiation-induced.

When a porogen is employed, it is present in the composition of thepresent invention in an amount of from about 0.1 to about 99.9% of thefunctionalized polymer. More preferably, the porogen is present in anamount of from about 5 to about 90% of the functionalized polymer.

A fourth component of the present invention is a photosensitive acidgenerator (PAG) that is compatible with the other components. Examplesof preferred PAGs include:-(trifluoro-methylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide(MDT), onium salts, aromatic diazonium salts, sulfonium salts,diaryliodonium salts, and sulfonic acid esters of N-hydroxyamides or-imides, as disclosed in U.S. Pat. No. 4,371,605. The content of the'605 patent is incorporated herein by reference. A weaker acid generatedfrom a PAG such as N-hydroxy-naphthalimide (DDSN) may be used.Combinations of PAGs may be used.

Condensation in the presence of an acid generated by a photoacidgenerator under exposure to radiation is not limited to silanols, butmay also include halosilanes, acetoxysilanes, silylamines, andalkoxysilanes. Organic crosslinking agents, such as those described inthe inorganic antireflective coating composition, includingtetramethoxymethyl glycoluril, methylpropyltetramethoxymethylglycoluril, methylphenyltetramethoxymethyl glycoluril, (available underthe POWDERLINK trademark from American Cyanamid Company) and2,6-bis(hydroxymethyl)-p-cresol, may also be included in theformulation. Although photoacid generators are preferred forcrosslinking, photobase generators can also be used for crosslinkingsilanol polymers.

The patternable low-k material of the present invention also includes acasting solvent to dissolve the other components. Examples of suitablecasting solvent include and is not limited to ethoxyethylpropionate(EEP), a combination of EEP and γ-butyrolactone, propylene-glycolmonomethylether alcohol and acetate, propyleneglycol monopropyl alcoholand acetate, and ethyl lactate. Combinations of these solvents may alsobe used.

In optimizing the photolithography process, an organic base may be addedto the formulation. The base employed in the present invention may beany suitable base known in the resist art. Examples of bases includetetraalkyammonium hydroxides, cetyltrimethylammonium hydroxide, and1,8-diaminonaphthalene. The compositions of the present invention arenot limited to any specific selection of base.

The term “acid-sensitive” is used throughout the application to denoteimageable functional groups which undergo a chemical reaction in thepresence of an acid generated by a photoacid generator under exposure toradiation. The acid-sensitive imageable functional groups employed inthe present invention may include acid-sensitive positive-tonefunctional groups or acid-sensitive negative-tone functional groups. Thenegative-tone acid-sensitive functional groups are functional groups forcausing a crosslinking reaction which causes the exposed areas to beinsoluble in a developer to form a negative-tone relief image afterdevelopment. The positive-tone acid-sensitive functional groups areacid-sensitive protecting groups which cause the exposed region to besoluble in a developer to form positive-tone relief images afterdevelopment.

The aforementioned patternable low-k materials act as photoresists usingpatterning; they can be positive-tone or negative-tone, and sensitive toG-line, I-line, DUV (248 nm, 193 nm, 157 nm, 126 nm, and EUV (13.4 μm).

Next, and as shown in FIG. 1C, the first patternable low-k dielectricmaterial 18 is pattern-wise exposed to form latent images of a desiredcircuitry. An optional post-exposure baking may be required to effectthe photochemical reactions. When performed, the baking step isconducted at a temperature from about 60° to about 200° C., with abaking temperature from about 80° to about 160° C. being even morepreferred. The duration of the baking step varies and is not critical tothe practice of the present invention. After exposure and post-exposurebaking, the latent images are developed into the low-k material with anappropriate developer, usually an aqueous base solution, such as 0.26Ntetramethylammoniahydroxide (TMAH) solution.

The pattern-wise exposing process can be accomplished in a variety ofways, including, for example, through a mask with a lithography stepperor a scanner with an exposure light source of G-line, I-line (365 nm),DUV (248 nm, 193 nm, 157 nm), Extreme UV (13.4 nm) an electron beam, oran ion beam. The pattern-wise exposing process also includes directwriting without the use of a mask with, for example, light, electronbeam, ion beam, and scanning probe lithography. Other patterningtechniques that can be used in the present invention include contactprinting techniques such as nanoimprint lithography, embroising, microcontact printing, replica molding, microtransfer molding, micromoldingin capillaries and solvent-assisted micromolding, thermal assistedembroising, inject printing, and the like.

Specifically, FIG. 1C illustrates the structure that is formed afterforming first interconnect patterns 20 within the patternable low-k film18. The first interconnect patterns 20 may include at least one viaopening (as shown and as preferred) or at least one line opening (notshown and less preferred than forming a via opening at this stage of theinventive method). As shown, the first interconnect patterns expose asurface of the ARC 16, if present.

After forming the first interconnect patterns, the low-k material 18 istypically, but not necessarily always, cured to form a cured low-kmaterial 18′ (See, FIG. 1C) in which the cured low-k material typicallyhas Si atoms that are bonded to cyclic rings (aliphatic or aromatic)through oxygen atoms. This type of bonding is evident from C¹³NMR or²⁹Si NMR. The curing is optional when the first patternable low-kmaterial is negative-tone, but it is required when the first patternablelow-k material is a positive-tone material.

Curing is performed in the present invention by a thermal cure, anelectron beam cure, an ultra-violet (UV) cure, an ion beam cure, aplasma cure, a microwave cure or a combination thereof. The conditionsfor each of the curing processes is well known to those skilled in theart and any condition can be chosen as long as it coverts thepatternable low-k material into a low-k film and maintains patternfidelity.

In another embodiment, the irradiation cure step is performed by acombination of a thermal cure and an ultra-violet (UV) cure wherein thewavelength of the ultra-violet (UV) light is from about 50 to about 300nm and the light source for the ultra-violet (UV) cure is a UV lamp, anexcimer (exciplex) laser or a combination thereof.

The excimer laser may be generated from at least one of the excimersselected from the group consisting of Ar₂*, Kr₂*, F₂, Xe₂*, ArF, KrF,XeBr, XeCl, XeCl, XeF, CaF₂, KrC, and Cl₂ wherein the wavelength of theexcimer laser is in the range from about 50 to about 300 nm.Additionally, the light of the ultra-violet (UV) cure may be enhancedand/or diffused with a lens or other optical diffusing device known tothose skilled in the art.

In one embodiment, this post patterning cure is a combined UV/thermalcure. This combined UV/thermal cure is carried on a UV/thermal curemodule under vacuum or inert atmosphere, such as N₂, He, Ar. Typically,the UV/thermal cure temperature is from about 100° C. to about 500° C.,with a cure temperature from about 300° to about 450° C. being moretypical. The duration of the UV/thermal cure is from about 0.5 min toabout 30 min with a duration from about 1 to about 10 min being moretypical. The UV cure module is designed to have a very low oxygencontent to avoid degradation of the resultant dielectric materials.

If the as-deposited inorganic antireflective coating 16 has been cured,the cure of the first patternable low-k material also converts theinorganic antireflective coating 16 into a dielectric material with adielectric constant less than 7.0.

After patterning and curing the first patternable low-k material 18, asecond patternable low-k material 22 is then formed providing thestructure shown in FIG. 1D. The second patternable low-k material 22 maycomprise the same or different material as the first patternable low-kmaterial 18. The deposition processes and thickness mentioned above forthe first patternable low-k material 18 are each applicable here for thesecond patternable low-k material 22. Typically, and in the embodimentillustrated, the first patternable low-k material 18 or the second low-kmaterial 22 is either a negative-tone or a positive-tone material.

Next, and as shown in FIG. 1E, the second patternable low-k dielectricmaterial 22 is patterned to include second interconnect patterns 24. Thepatterning of the second patternable low-dielectric material 22 isperformed utilizing the same basic processing equipment and steps asthose used for patterning the first patternable low-k dielectricmaterial. In the illustrated embodiment, the second interconnect patternis typically a line. The second interconnect pattern may also be a via,when the first interconnect pattern is a line.

After patterning the second patternable low-k material 22, the structureis cured providing the structure shown in FIG. 1F. In FIG. 1F, referencenumeral 22′ denotes the cured second low-k material. Like the firstcured low-k material 18′, the cured second low-k material 22′ has adielectric constant within the ranges mentioned above and it also ischaracterized as typically having Si atoms bonding to cyclic rings(aliphatic or aromatic) via oxygen atoms. If not previously cured, thiscuring step also cures the first patternable low-k material 18 into acured low-k material 18′ typically having the Si bonding mentionedabove. The cure methods, equipment and processes mentioned above for thefirst patternable low-k material 18 are each applicable here for thesecond patternable low-k material 22.

Further interconnect processing is then performed on the structure inFIG. 1F providing the structure shown in FIG. 2. This includes etchingthrough the ARC 16 and dielectric cap 14 if present, utilizing anetching process such as, for example, reactive ion etching, or gascluster ion beam etching. Next, a diffusion barrier liner (not shown),which may comprise Ta, TaN, Ti, TiN, Ru, RuTaN, RuTa, W, WN or any othermaterial that can serve as a barrier to prevent conductive material fromdiffusing there through, is typically formed into the first and secondinterconnect patterns by a deposition process such as, for example,atomic layer deposition (ALD), chemical vapor deposition (CVD), plasmaenhanced chemical vapor deposition (PECVD), physical vapor deposition(PVD), sputtering, chemical solution deposition, or plating. In someembodiments (not shown), the diffusion barrier liner may comprise acombination of layers. The thickness of the diffusion barrier liner mayvary depending on the exact means of the deposition process employed aswell as the material and number of layers employed. Typically, thediffusion barrier liner has a thickness from about 4 to about 40 nm,with a thickness from about 7 to about 20 nm being more typical.

Following the formation of the diffusion barrier liner, the remainingregion of the first and second interconnect patterns is filled with aconductive material 25 forming a conductive feature. The conductivematerial 25 used in forming the conductive feature includes, forexample, polySi, a conductive metal, an alloy comprising at least oneconductive metal, a conductive metal silicide, a conductive nanotube ornanowire or combinations thereof. Preferably, the first conductivematerial 25 that is used in forming the conductive feature is aconductive metal such as Cu, W or Al, with Cu or a Cu alloy (such asAlCu) being highly preferred in the present invention. The conductivematerial 25 is filled into the remaining first and second interconnectpatterns utilizing a conventional deposition process including, but notlimited to CVD, PECVD, sputtering, chemical solution deposition orplating.

After deposition, a conventional planarization process such as, forexample, chemical mechanical polishing (CMP) can be used to provide astructure in which the diffusion barrier liner and the conductivematerial 25 each have an upper surface that is substantially coplanarwith the upper surface of the cured second low-k material 22′.

After forming the at least one conductive material 25, anotherdielectric cap (not shown) is formed on the surface of the cured secondlow-k material 22′ utilizing a conventional deposition process such as,for example, CVD, PECVD, chemical solution deposition, or evaporation.The dielectric cap comprises any suitable dielectric capping materialsuch as, for example, SiC, SiN, SiO₂, a carbon doped oxide, a nitrogenand hydrogen doped silicon carbide SiC(N,H) or multilayers thereof. Thisdielectric cap can be a continuous layer or a discontinuous layer. Itcan also be a select cap, such as CoWP, on metal only. The thickness ofthe dielectric cap may vary depending on the technique used to form thesame as well as the material make-up of the layer. Typically, thedielectric cap has a thickness from about 15 to about 55 nm, with athickness from about 25 to about 45 nm being more typical.

In addition to the dual-damascene embodiment mentioned above, thepresent invention also contemplates a single-damascene embodiment whichwill now be described in greater detail in reference to FIGS. 3A-3D.

FIG. 3A shows an initial structure 10 that can be used in thisembodiment of the present invention. The initial structure 10 shown inFIG. 3A is identical to the initial structure shown in FIG. 1A.Specifically, the initial structure shown in FIG. 3A also includes asubstrate 12, an optional dielectric cap 14 located on a surface of thesubstrate 12, and an ARC 16 located on the surface of the dielectric cap14. The materials, deposition methods, and thickness of each ofsubstrate 12, optional dielectric cap 14 and ARC 16 are the same as thatdescribed above for the dual-damascene embodiment of the presentinvention.

FIG. 3B shows the structure of FIG. 3A after forming a patternable low-kmaterial 18 directly on the surface of the ARC 16. The patternable low-kmaterial 18 may be a positive-tone material or a negative-tone material.The composition of the patternable low-k material 18 in this embodimentof the invention is the same as that mentioned above in thedual-damascene embodiment. Also, the patternable low-k material 18 isformed as described above and it has a thickness within the rangesmentioned above as well.

FIG. 3C illustrates the structure after forming interconnect patterns 20within the patternable low-k film 18. The interconnect patterns 20 mayinclude at least one via opening (as shown and as preferred) or at leastone line opening. As shown, the first interconnect pattern exposes asurface of the ARC 16, if present. The formation of the interconnectpatterns 20 into the patternable low-k material 18 includes thepatterning process mentioned above in the dual-damascene embodiment.

FIG. 3D illustrates the structure that is formed after curing thepatternable low-k material 18 into cured low-k material 18′. The curedlow-k material 18′ has a dielectric constant within the ranges mentionedabove and it also typically has Si atoms are bonded to cyclic rings(aliphatic or aromatic) via oxygen atoms. In the uncured state, suchbonding is not observed. The cure methods, equipment and processesmentioned above for the patternable low-k material 18 in the dualdamascene embodiment are each applicable here for the patternable low-kmaterial 18 in this singe damascene embodiment.

If the as-deposited inorganic antireflective coating 16 has been cured,the cure of the patternable low-k material also converts the inorganicantireflective coating 16 into a dielectric material with a dielectricconstant less than 7.0.

FIG. 4 illustrates the structure that is formed after furtherinterconnect process steps including at least filling the interconnectpatterns with a conductive material 25 and planarizing the same. Thefurther processing steps of the present invention have been described ingreater detail in regard to the dual-damascene embodiment. It should benoted that although FIG. 4 does not show the interconnect openings toextending through the ARC layer 16 and the cap layer 14, depending onthe underlying substrate and connections required thereto, such openingscan be provided using the means described in the dual-damasceneembodiment.

The following examples are provided to illustrate some embodiments ofthe present invention.

Example 1 Single-Damascene Integration of Negative-Tone PatternableLow-k Dielectric (k=2.7) On-Chip Electrical Insulator Example 1AInorganic Spin-On Antireflective Layer for Patternable Low-k Resist-1(PPLKARC01)

An inorganic spin-on antireflective coating composition was formulatedwith the following components: 1.5 g of 9-anthracenemethanol boundedpoly(4-hydroxybenzylsilsesquioxane) with 20% of 9-anthracenemethanol,0.176 g of glycoluril resin (POWDERLINK cross-linking agent), 0.088 g ofK-Pure 2678 (thermal acid generator from King Industry), 0.1 g of FC430surfactant (10 wt % PGMEA solution sold by 3M Corporation) and 33.429 gof propylene glycol monomethyl ether acetate (PGMEA) to form a solutionwith a 5 wt. % of total solid content. The resulting formulation wasfiltered through a 0.2 micron filter.

Example 1B Inorganic spin-On Antireflective Layer for Patternable Low-kResist-2 (PPLKARC02)

An inorganic spin-on antireflective coating composition was formulatedwith the following components: 1.5 g of 9-anthracenemethanol boundedpoly(4-hydroxybenzylsilsesquioxane) with 15% of 9-anthracenemethanol,0.176 g of glycoluril resin (POWDERLINK cross-linking agent), 0.088 g ofK-Pure 2678 (thermal acid generator from King Industry), 0.1 g of FC430surfactant (10 wt % PGMEA solution sold by 3M Corporation) and 33.429 gof propylene glycol monomethyl ether acetate (PGMEA) to form a solutionwith a 5 wt. % of total solid content. The resulting formulation wasfiltered through a 0.2 micron filter.

1. Inorganic Spin-On ARC Process

The inorganic spin-on antireflective coating composition in Example 1A(PPLKARC01) was deposited on a 200 mm silicon wafer having a 350 Å NBLOKtop layer on a TEL MARK 8 track at 2000 rpm for 30 see and post applybased at 150° C. for 120 sec.

2. Patternable Low-k Material

A patternable low-k composition was formulated with 60 g of a 20 wt %solution of 6:4 pHMBS/MBS in propylene glycol monomethyl ether acetate(PGMEA), 40 g of a 20 wt % solution of the silsesquioxane copolymerLKD-2021, 2 g of a 20 wt % solution of triphenylsulfonium nonaflate inPGMEA, and 2 g of a 0.5 wt % solution of an organic base such astrioctylamine in PGMEA. The resulting patternable low-k formulation wasfiltered through a 0.2 micron filter.

3. Litho Process

A patternable low-k composition formulated above was spin coated (2000rpm for 30 seconds) on top of the inorganic spin-on ARC layer on a 200mm silicon wafer to produce an approximately 0.6 μm film. The wafer andfilm were pre-exposure baked at about 110° C. for 60 seconds (s),pattern-wise exposed to 248 nm deep ultraviolet (DUV) light on an ASML(0.63 NA, 3/6 annular) DUV stepper with a chrome on glass mask, and thenpost exposure baked at 110° C. for 60 sec. This was followed by two 30second puddle development steps with 0.26 N TMAH developer to resolve250 nm line and space features at a radiant energy dose of 24 mJ/cm².

4. UV Cure Process

The wafer with 250 nm line and space pattern was subjected to aUV-thermal cure in a 200 mm Applied Materials Producer broadband UV curetool. The process conditions were 400° C. for 10 min under a N₂atmosphere and a pressure of 8 Torr. This UV thermal cure converted thepatternable low-k resist and the inorganic ARC layer into a low-kdielectric materials. It also maintained the patternable low-k resistfeatures obtained during the lithographic process. It further improvedthe sidewall angle of the patternable low-k resist features. Thedielectric constant of this patternable low-k composition cured underthis condition is 2.7.

5. Analysis

-   -   a. X-section SEM    -   The post UV cure SEM of the patternable low-k dielectric        structure was taken on a LEO low voltage SEM.    -   b. Cu/Low-K X-Section    -   The patternable low-k/Cu interconnect structure was        cross-sectioned and examined in a Hitachi SEM. The        cross-sectioned surface was polished, decorated with a diluted        HF aqueous solution.

Example 2 Single-Damascene Integration of Negative-Tone PatternableLow-k Dielectric (k=2.7) On-Chip Electrical Insulator

1. Material Composition

A patternable low-k composition was formulated with 60 g of a 20 wt %solution of 6:4 pHMBS/MBS in propylene glycol monomethyl ether acetate(PGMEA), 40 g of a 20 wt % solution of the silsesquioxane copolymerLKD-2021, 2 g of a 20 wt % solution of triphenylsulfonium nonaflate inPGMEA, and 2 g of a 0.5 wt % solution of an organic base such astrioctylamine in PGMEA. The resulting patternable low-k formulation wasfiltered through a 0.2 micron filter.

The inorganic spin-on antireflective coating composition in Example 1A(PPLKARC01) was deposited on a 200 mm silicon wafer having a 350 Å NBLOKtop layer on a TEL MARK 8 track at 2000 rpm for 30 sec and post applybased at 150° C. for 120 sec.

2. Litho Process

The patternable low-k composition formulated above was spin coated (2000rpm for 30 seconds) on top of the inorganic spin-on ARC layer on a 200mm silicon wafer to produce an approximately 0.6 μm film. The wafer andfilm were pre-exposure baked at about 110° C. for 60 seconds,pattern-wise exposed to 248 nm deep ultraviolet (DUV) light on an ASML(0.63 NA, 3/6 annular) DUV stepper with a chrome on glass mask, and thenpost exposure baked at 110° C. for 60 seconds. This was followed by two30 second puddle development steps with 0.26 N TMAH developer to resolve250 nm line and space features at a radiant energy dose of 24 mJ/cm².

3. UV Cure Process

The wafer with 250 nm line and space pattern was subjected to aUV-thermal cure in a 200 mm Applied Materials Producer broadband UV curetool. The process conditions were 400° C. for 10 min under a N₂atmosphere and a pressure of 8 Torr.

4. Liner Process

Liner and Cu seed were deposited in a 200 mm Endura Encore Ta/TaN toolfrom Applied Materials. About 95 Å TaN, 190 Å Ta, and 600 Å Cu seed weredeposited sequentially.

5. Cu plating and Annealing

This wafer was electrochemically plated on SEMITOOL tool to fill thetrenches with about 750 nm Cu. The as-plated wafer was annealed at 350°C. for 1 hr in a N₂ atmosphere in a copper anneal oven.

6. Cu CMP Process

The excessive Cu was removed by chemical-mechanical polishing with anEbara Frex Polisher. The polishing was conducted in stages with a V3high-abrasive slurry. The total polish time was For Cu CMP, V3:HighAbrasive; Totalo polish time 45 sec.

7. NBLoK Cap

A 350 Å of NBLOK cap layer was deported on top of the polishedpatternable low-K/Cu interconnect with a 200 mm CVD tool (Centura) fromApplied Materials Inc.

8. Analysis

a. X-Section SEM

-   -   The post UV cure SEM of the patternable low-k dielectric        structure was taken on a LEO low voltage SEM.

b. Cu/Low-K X-Section

-   -   The patternable low-k/Cu interconnect structure was        cross-sectioned and examined in a Hitachi SEM. The        cross-sectioned surface was polished, decorated with a diluted        HF aqueous solution.

While the present invention has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present invention. It is therefore intended that the presentinvention not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

1. A method of fabricating an interconnect structure comprising:providing at least one patternable low-k material on a surface of aninorganic antireflective coating (ARC) that is located atop a substrate,said inorganic antireflective coating is liquid deposited and comprisesa polymer that has at least one monomer unit comprising the formula M-R¹wherein M is at least one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and Laand R¹ is a chromophore; forming at least one interconnect patternwithin said at least one patternable low-k material, said at least oneinterconnect pattern is formed without utilizing a separate photoresistmaterial; and curing said at least one patternable low-k material andthe inorganic ARC into materials having a dielectric constant of notmore than 4.3 and 7.0, respectively.
 2. The method of claim 1 whereinsaid inorganic antireflective coating further includes at least onesecond monomer unit, said at least one second monomer unit has theformula M′-R², wherein M′ is at least one of Si, Ge, B, Sn, Fe, Ta, Ti,Ni, Hf and La and R² is a cross-linking agent.
 3. The method of claim 1further comprising at least one additional component, including aseparate crosslinker, an acid generator or a solvent.
 4. The method ofclaim 1 wherein said at least one patternable low-k material comprises afunctionalized polymer having one or more irradiation/acid-sensitiveimageable groups.
 5. The method of claim 4 wherein said functionalizedpolymer comprises a polymer of a hydrocarbon, a fluorinated hydrocarbon,a siloxane, a silane, a carbosilane, an oxycarbosilane, anorganosilicate or a silsesquioxane.
 6. The method of claim 1 whereinsaid curing comprises a thermal cure, an electron beam cure, an UV cure,an ion beam cure, a plasma cure, a microwave cure or any combinationthereof.
 7. The method of claim 1 further comprising forming aconductive material within said at least one interconnect pattern.
 8. Amethod of fabricating a dual-damascene interconnect structurecomprising: providing a first patternable low-k material on a surface ofan inorganic antireflective coating (ARC) that is located atop asubstrate, said inorganic antireflective coating is liquid deposited andcomprises a polymer that has at least one monomer unit comprising theformula M-R¹ wherein M is at least one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni,Hf and La and R¹ is a chromophore; forming first interconnect patternswithin the patternable low-k material without a separate photoresistmaterial; providing a second patternable low-k material on top of thefirst patternable low-k material including said first interconnectpatterns; forming second interconnect patterns within said secondpatternable low-k material without a separate photoresist material; andcuring at least said second patternable low-k material and the inorganicARC into materials having a dielectric constant of not more than 4.3 and7.0, respectively.
 9. The method of claim 8 wherein said inorganicantireflective coating further includes at least one second monomerunit, said at least one second monomer unit has the formula M′-R²,wherein M′ is at least one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and Laand R² is a cross-linking agent.
 10. The method of claim 8 furthercomprising at least one additional component, including a separatecrosslinker, an acid generator or a solvent.
 11. The method of claim 8wherein said first and second patternable low-k materials are the sameor different and comprise functionalized polymers having one or moreirradiation/acid-sensitive imageable groups.
 12. The method of claim 11wherein said functionalized polymers comprise polymers of hydrocarbons,fluorinated hydrocarbons, siloxanes, silanes, carbosilanes,oxycarbosilanes, organosilicates or silsesquioxanes.
 13. The method ofclaim 8 wherein said curing at least said second patternable low-kmaterial comprises a thermal cure, an electron beam cure, an UV cure, anion beam cure, a plasma cure a microwave cure or any combinationthereof.